The objective of this study is to determine the doses of VPA-985, a selective non-peptide antagonist of vasopressin-2 receptors, that safely and efficaciously increase serum sodium in patients with hyponatremia of diverse etiologies. Secondary objectives are to compare efficacy in an outpatient and inpatient setting and to determine if correction of the hyponatremia improves cognitive function or other measures of clinical benefit. The design is a randomized, double-blind, parallel group, placebo controlled, multi-center, inpatient and outpatient study. The subjects will be patients, age 18-80, with chronic hyponatremia due to liver failure or SIADH. After pre-study screening, they will be admitted to the GCRC and randomly assigned to receive placebo or one of three doses of the VPA-985 twice daily for seven days. Fluid intake will be restricted and serum sodium, body weight, urine output, vital signs and physical condition will be determined daily. Vasopressin and other hormones will be measured before and after the treatment. If clinically indicated, the patient will be discharged on the same treatment and followed in the outpatient clinic for two weeks. The treatment then will be stopped and the final post-treatment examination given. Cognitive function tests will be performed before and after the inpatient and outpatient phase. All tests except plasma sodium will be performed or scored by a central laboratory, and the results will be analyzed by Wyeth-Ayerst.